1. Field of the Invention
The present invention relates to an injection molding resin-type printed wiring board having an electrical circuit pattern layer formed integrally on its surface.
2. Description of the Prior Art
Japanese Laid-Open Patent No. 60-121791, for example, has disclosed a technique in which a printed wiring pattern in the form of a transfer sheet is preliminarily set in a board injection mold so that simultaneously with the injection molding of a resin, the wiring pattern is formed on the surface of a molded product board.
In the past, injection molding resin materials used for this type of molded printed wiring boards have been the so-called super engineering plastics such as polysulfone, polyether sulfone and polyether imide and it has been true that these materials have the disadvantage of being high in cost.
A molding resin material meeting the required functions of such molded printed wiring board by the injection molding method, is required to satisfy various requirements that the board is small in warpage and torsion during the molding and solder mounting, that the electrical characteristics are satisfactory as the printed wiring board, that there is less danger of change in dimension, shape and electrical characteristics due to the absorption of moisture, that there is no danger of causing such damages as deformation and breaks in the printed wiring pattern on a transfer sheet set in the mold cavity during the injection operation, that good adhesion is ensured between the printed wiring board and the printed wiring pattern on the transfer sheet by the injection molding, that the product surface has an excellent external appearance and tinting properties when concurrently used as an outer component such as a housing and so on.